The present invention relates to a jack module for optical transmission, and more particularly, to a jack module into which specified plugs are to be inserted for inputting and outputting (relaying included, which is applicable throughout hereinafter) optical signals to and from electronic equipment.
The invention also relates to a plug-and-jack type optical transmission apparatus in which a signal-transmission cable having specified plugs at both ends, and a pair of optical-transmission jack modules for inputting and outputting optical signals, are combined together so that communications in the half-duplex method can be performed through the signal-transmission cable between electronic equipments having the jack modules respectively.
Still also, the invention relates to a jack module for both optical and electrical use, and a plug-and-jack type transmission apparatus for both optical and electrical use, having a construction that the jack module for optical transmission or the plug-and-jack type optical transmission apparatus is provided with electrical connection terminals for discriminating the type of a plug inserted thereinto and for inputting and outputting electric signals via the plug.
In this specification, the terms, “electronic equipment,” refer to a wide range of equipment that handles electronic information such as CDs (Compact Discs), MDs (Mini Discs), DATs (Digital Audio Tapes), DVDs (Digital Video Discs), computers and PDAs (personal digital assistants), etc. In addition, the terms, “electronic information,” include not only digital information but also analog information.
Conventionally, there has been known a jack module for both optical and electrical use having a construction that, as shown in FIGS. 9A and 9B, a holder body 102 into which a plurality of specified types of plugs are to be inserted is provided with an optical semiconductor device 103 for inputting and outputting optical signals and a plurality of electrical connection terminals 40 for discriminating the type of a plug inserted thereinto and for inputting and outputting electric signals (where the whole unit of the jack module is denoted by reference numeral 101) (e.g., Japanese Patent Laid-Open Publication H06-140106). FIG. 9A shows an example in which a small-size single-head electric plug (for analog electric signals) 10 is inserted, and FIG. 9B shows an example in which an optical fiber plug 30 is inserted.
The optical semiconductor device 103 is so formed that a light-emitting chip 105 and a driver IC (Integrated Circuit) chip 106 for driving this light-emitting chip 105 are mounted on one side 104a of a lead frame 104, where these component members are molded into a generally rectangular parallelopiped shape with a transparent resin (sealing resin) 107. The chip-mounted surface 104a of the lead frame 104 is disposed vertical to a center axis X of the plug to be inserted. In the illustrated optical semiconductor device 103, which is to be provided on the transmission side of one-way communications, the light-emitting chip 105 is disposed on an extension of the center axis X of the plug, and the driver IC chip 106 is disposed in its neighborhood. In contrast to this, in the case of jack module, which is to be provided on the reception side of one-way communications, a light-receiving chip is disposed on an extension of the center axis X of the plug, and a signal-processing IC chip which handles the output of the light-receiving chip is disposed in its neighborhood. The rest of the construction is the same as that of the transmission side.
The electrical connection terminals 40 are disposed in a plurality along the center axis X of the plug to be inserted. The plugs that are intended for insertion include, as shown in FIG. 10A, an electric plug 10 for analog electric signals, an electric plug 20 for digital electric signals, and an optical fiber plug 30 for inputting and outputting digital optical signals. The electric plug 10 for analog electric signals has, in an order from its fore end, a chip portion 11 for inputting and outputting a left (L) signal, an insulated collar portion 12, a ring portion 13 for inputting and outputting a right (R) signal, an insulated collar portion 14, and a sleeve portion 15 of ground (GND) potential. The electric plug 20 for digital electric signals has, in an order from its fore end, a chip portion 21 for inputting and outputting a plus (+) signal, an insulated collar portion 22, a ring portion 23 for inputting and outputting a minus (−) signal, an insulated collar portion 24, a sleeve portion 25 of ground (GND) potential, and an insulated sleeve portion 26. The optical fiber plug 30 has, in an order from its fore end, a chip portion 31 and a sleeve portion 32. In this optical fiber plug 30, an optical fiber 33 passes through at its center, while an end face 33a of the optical fiber 33 is exposed at a fore end of the chip portion 31.
Outside dimensions of these plugs 10, 20, 30 are set to the same ones according to the standards so as to be insertable to the same jack module. Each chip portion is formed into a fusiform shape, and each ring portion and each sleeve portion are formed into a cylindrical shape. The sleeve portion 15 of the electric plug 10 for analog electric signals is provided over a range corresponding to a range over which the insulated sleeve portion 25 and the sleeve portion 26 of the electric plug 20 for digital electric signals are provided.
In correspondence to the above structure of the plugs 10, 20, 30, as shown in FIG. 10B, the electrical connection terminals of the jack module 101 are placed at four positions along the center axis X of the plug to be inserted, respectively. That is, with regard to the electric plug 20 for digital electric signals, which has the largest number of divisions, an electrical connection terminal 41 is placed at a first position for contact with the chip portion 21, and so are an electrical connection terminal 42 at a second position for contact with the (−) ring portion 23, electrical connection terminals 43A, 43B at a third position for contact with the GND sleeve portion 25, and an electrical connection terminal 44 at a fourth position for contact with the insulated sleeve portion 26.
For discrimination of the type of a plug that has been inserted, a reference voltage Vref is applied via current limiting resistors r to the electrical connection terminals 43A, 43B placed at the third position and the electrical connection terminal 44 placed at the fourth position, respectively. Further, the electrical connection terminal 43A, which is one of the electrical connection terminals placed at the third position, is grounded. Given that voltages of these terminals 43A, 43B and 44 are V1, V2 and V3, respectively, these voltages V1, V2 and V3 are at such levels as shown in FIG. 10C according to the types of inserted plugs (where high level is represented by “H” and low level by “L”). Accordingly, if the inserted plug is the electric plug 10 for analog electric signals, then the voltages V1, V2 and V3 are all at “L”. If the inserted plug is the electric plug 20 for digital electric signals, then the voltages V1, V2 and V3 are at “L”, “L” and “H”, respectively. If the inserted plug is the optical fiber plug 30, then the voltages V1, V2 and V3 are at “L”, “H” and “H”, respectively. In addition, if no plug is inserted, the voltages V1, V2 and V3 are all at “H”. Therefore, the type of an inserted plug can be discriminated based on these voltages V1, V2 and V3.
If the inserted plug is the electric plug 10 for analog electric signals or the electric plug 20 for digital electric signals, then electric signals can be inputted and outputted via the electrical connection terminal 41 placed at the first position and the electrical connection terminal 42 placed at the second position. During communications in electric signals, the optical semiconductor device 103 shown in FIG. 9 holds in a halt state.
Meanwhile, if the inserted plug is the optical fiber plug 30 as shown in FIG. 9B, the optical semiconductor device 103 becomes operative. In this example, signal light emitted from the light-emitting chip 105 is converged by a lens portion 107a formed at the surface of the sealing resin 107, coming incident on the internal of the optical fiber 33 through the end face 33a of the optical fiber plug 30. Then, the incident light is transmitted through the optical fiber cable 50, reaching a reception-side jack module for both optical and electrical use via an unshown optical fiber plug (of the same structure as the optical fiber plug 30) provided at the other end of the optical fiber cable 50. As already described, in the reception-side jack module, the optical semiconductor device is so constructed that a light-receiving chip is disposed on an extension of the center axis X of the plug, and a signal-processing IC chip which handles outputs of the light-receiving chip is disposed in its neighborhood. Accordingly, signal light emitted from the end face of the optical fiber plug comes incident on the light-receiving chip, and is subjected to signal processing by the signal-processing IC chip. During communications in optical signals, the electrical connection terminals 40 hold in a halt state.
In this connection, since the communications method using the above jack module are one-way communications, implementing two-way communications involves two transmission cables each having plugs at both ends and a total of four jack modules into which the plugs are to be inserted, respectively. This causes increases in component parts, leading to increases in the apparatus scale, disadvantageously.
Therefore, it has recently been attempted that in a jack module, light-emitting chip and light-receiving chip are disposed in juxtaposition on a plane vertical to the center axis of the plug to be inserted, in order to implement full-duplex (simultaneous two-way) communications. In this full-duplex communications method, two-way communications are enabled with one transmission cable having plugs at both ends, and a total of two jack modules into which each plug is to be inserted. However, the full-duplex communications method encounters a problem of noise occurrence due to optical crosstalk (a phenomenon that an optical output of a light-emitting chip is reflected to go incident on a light-receiving chip in the same jack module) Taking measures for effects of this optical crosstalk causes complexities in apparatus construction and signal processing, which in turn causes increases in the load for signal processing. This would result in increases in size and price of the apparatus.
On the other hand, in the half-duplex communications method (a method in which communications are in one way at some instant, but two-way communications are performed by switching), two-way communications can be implemented with one transmission cable having plugs at both ends, and a total of two jack modules into which the plugs are to be inserted, respectively, and moreover the problem of optical crosstalk does not occur.
These problems come to issues not only with jack modules for both optical and electrical use, but also with jack modules that perform optical transmission but that do not necessarily have electrical connection terminals (which jack modules are generically referred to as “jack modules for optical transmission”).